Table 1 – Priority group 1 power station features Power Station Year Commissioned General Description Lake Echo 1956 1595m of 2.5m to 2.9m diameter steel penstock. 7.315m diameter steel surge tower. 2.90m diameter self-closing butterfly HTV. 1.524m diameter straight flow MIV. 1/33.5MW Francis turbine with 0.838m diameter TRV. Wayatinah 1957 3320m concrete lined rock tunnel. 1273m of 4.11m diameter twin woodstave pipelines. 16.764m diameter steel surge tower. 3/2.90m diameter self-closing butterfly HTVs. 3/3.2m diameter steel penstocks each 230m in length. 3/2.74m diameter butterfly MIVs. 3/15MW Francis turbines with 0.828m diameter TRVs. Tarraleah 1938 – 1943 2135m of 2.6m diameter twin steel pipelines. Twin 5.486m diameter steel surge towers. 6/1.529m diameter self-closing butterfly HTVs. 6/584m 1.2m to 1.5m diameter steel penstocks. 3/1.219m diameter cylindrically balanced MIVs. 3/1.016m diameter latticed butterfly MIVs. 3/English Electric 18MW Pelton turbines with diffusers. 3/Boving 18MW Pelton turbine with deflectors.